DAMAGE STUDIES OF BRITTLE-DUCTILE TRANSITION IN PP/EPDM BLENDS

Damage zones of brittle-ductile (B-D) transition in PP/EPDM blends are studied in this paper. The contribution of crazing and shear yielding zones in damage zones to energy dissipation of blends was measured with computer image analysis (CIA) and the transition of shear yielding zone (A(sh)) with rubber volume fraction (V-f) was also manipulated. Results showed that the B-D transition of impact strength of blends corresponded to the fracture mechanism in PF/EPDM blends, from matrix crazing to matrix shear yielding. In addition, two new parameters, density of energy dissipation for crazing zone (F-cz) and for shear yielding zone (F-sh), are first obtained in this paper. The value of F-sh is about four times larger than that of F-cz for PP/EPDM blends, which confirmed that the matrix shear yielding is a more effective way of energy dissipation in blends.